Effect of leaf wetness duration and temperature on infection of downy mildew (Peronospora sp.) of basil

Abstract

The effect of leaf wetness duration and temperature on the development of downy mildew of basil, incited by Peronospora sp., was studied under controlled conditions. In several trials carried out under growth chamber and or glasshouse conditions, downy mildew was particularly severe when plants were kept wet for a period of at least 6-12 h immediately after inoculation. The pathogen was mostly active at a temperature of 20†C. At temperatures of 12†C and of 27†C no disease development was observed. A leaf wetness of at least 24 h after symptom appearance is necessary for sporulation. The results obtained are critically discussed also in relation to the possibility of managing this disease through proper cultural practices.